Sapphire

Little has changed in the way Java desktop UI is written since the original Java release.
Technologies have changed (AWT, Swing, SWT, etc.), but fundamentals remain the same. The developer
must choose which widgets to use, how to lay those widgets out, how to store the data being edited
and how to synchronize the model with the UI. Even the best developers fall into traps of having UI
components talk directly to other UI components rather than through the model. Inordinate amount of
time is spent debugging layout and data-binding issues.

Sapphire aims to raise UI writing to a higher level of abstraction. The core premise is that the
basic building block of UI should not be a widget (text box, label, button, etc.), but rather a
property editor. Unlike a widget, a property editor analyzes metadata associated with a given
property, renders the appropriate widgets to edit that property and wires up data binding. Data is
synchronized, validation is passed from the model to the UI, content assistance is made
available, etc.

This fundamentally changes the way developers interact with a UI framework. Instead of writing
UI by telling the system how to do something, the developer tells the system what they intend to
accomplish. When using Sapphire, the developer says "I want to edit LastName property of the person
object". When using widget toolkits like SWT, the developer says "create label, create text box,
lay them out like so, configure their settings, setup data binding and so on". By the time the
developer is done, it is hard to see the original goal in the code that's produced. This results
in UI that is inconsistent, brittle and difficult to maintain.

First, The Model

Sapphire includes a modeling framework that is tuned to the needs of the Sapphire UI
framework and is designed to be easy to learn. It is also optimized for iterative development.
A Sapphire model is defined by writing Java interfaces and using annotations to attach metadata.
An annotation processor that is part of Sapphire SDK then generates the implementation classes.
Sapphire leverages Eclipse Java compiler to provide quick and transparent code generation that
runs in the background while you work on the model. The generated classes are treated as build
artifacts and are not source controlled. In fact, you will rarely have any reason to look at
them. All model authoring and consumption happens through the interfaces.

In this article we will walk through a Sapphire sample called EzBug. The sample is based
around a scenario of building a bug reporting system. Let's start by looking at IBugReport.

As you can see in the above code listing, a model element definition in Sapphire is composed of a series
of blocks. These blocks define properties of the model element. Each property block has a PROP_* field that declares
the property, the metadata in the form of annotations and the accessor methods. All metadata about the
model element is stored in the interface. There are no external files. When this interface is
compiled, Java persists these annotation in the .class file and Sapphire is able to read them
at runtime.

Sapphire has four types of properties: value, element, list and transient. Value properties hold simple data,
such as strings, integers, enums, etc. Any object that is immutable and can be serialized to a string can
be stored in a value property. An element property holds a reference to another model element. You can
specify whether this nested model element should always exist (implied element property) or if it should be possible to create and
delete it. A list property holds zero or more model elements. A list can be homogeneous (only holds one
type of elements) or heterogeneous (holds elements of various specified types). A transient property holds an
arbitrary object reference that does not need to be persisted to permanent storage.

Using a combination of list and element properties, it is possible to create an arbitrary model hierarchy. In the
above listing, there is one list property. It is homogeneous and references IHardwareItem element type. Let's
look at that type next.

The IHardwareItem listing should look very similar to IBugReport and that's the point. A Sapphire model
is just a collection of Java interfaces that are annotated in a certain way and reference each other.

A bug report is contained in IFileBugReportOp, which serves as the top level type in the model.

You can use any enum as a type for a Sapphire value property. Here, once again, you
see Sapphire pattern of using Java annotations to attach metadata to model particles.
In this case the annotations are specifying how Sapphire should present enum items
to the user and how these items should be serialized to string form.

Then, The UI

The bulk of the work in writing UI using Sapphire is modeling the data that you want to
present to the user. Once the model is done, defining the UI is simply a matter of
arranging the properties on the screen. This is done via an XML file.

A Sapphire UI definition is a hierarchy of parts. At the lowest level we have the property editor and a few other basic
parts like separators. These are aggregated together into various kinds of composities until the entire part hierarchy
is defined. Some hinting here and there to guide the UI renderer and the UI definition is complete. Note the top-level
composite and dialog elements. These are parts that you can re-use to build more complex UI definitions or reference
externally from Java code.

Next we will write a little bit of Java code to open the dialog that we defined.

Pretty simple, right? We create the model and then use the provided SapphireDialog class to instantiate the UI by
referencing the model instance and the UI definition. The pseudo-URI that's used to reference the UI definition
is simply bundle id, followed by the path within that bundle to the file holding the UI definition, followed by
the id of the definition to use.

Let's run it and see what we get...

There you have it. Professional rich UI backed by your model with none of the fuss of configuring widgets,
trying to get layouts to do what you need them to do or debugging data binding issues.

One Step Further

A dialog is nice, but really a wizard would be better suited for filing a bug report. Can Sapphire do that?
Sure. Let's first go back to the model. A wizard is a UI pattern for configuring and then executing an operation.
Our model is not really an operation yet. We can create and populate a bug report, but then we don't know what to do
with it.

Any Sapphire model element can be turned into an operation by adding an execute method. We will do that
now with IFileBugReportOp. In particular, IFileBugReportOp will be changed to extend IExecutableModelElement
and will acquire the following method definition:

Note how the execute method is specified. We don't want to modify the generated code to implement it, so we use
delegation instead. The @DelegateImplementation annotation can be used to delegate any method on a model
element to an implementation located in another class. The Sapphire annotation processor will do the necessary
hookup.

SapphireWizard will invoke the operation's execute method when the wizard is finished. That means we don't have
to act based on the result of the open call. The execute method will have completed by the time the open method returns
to the caller.

The above code pattern works well if you are launching the wizard from a custom action, but if you need to contribute
a wizard to an extension point, you can extend SapphireWizard to give your wizard a zero-argument constructor that creates
the operation and references the correct UI definition.

Let's run it...

One More Step

Now that we have a system for submitting bug reports, it would be nice to have a way to maintain a collection of these reports.
Even better if we can re-use some of our existing code to do this. Back to the model.

The first step is to create IBugDatabase type which will hold a collection of bug reports. By now you should
have a pretty good idea of what that will look like.

Sapphire simplifies creation of multi-page editors. It also has very good integration with WTP XML editor that makes it easy
to create the very typical two-page editor with a form-based page and a linked source page showing the underlying XML. The
linkage is fully bi-directional.

To create an editor, we start by defining the structure of the pages that will be rendered by Sapphire. Sapphire currently
only supports one editor page layout, but it is a very flexible layout that works for a lot scenarios. You get a tree outline
of content on the left and a series of sections on the right that change depending on the selection in the outline.

You can see that the definition centers around the outline. The definition traverses the model as the
outline is defined with sections attached to various nodes acquiring the context model element from their node.
The outline can nest arbitrarily deep and you can even define recursive structures by factoring out
node definitions, assigning ids to them and then referencing those definitions similarly to how this
sample references an existing composite definition.

The next step is to create the actual editor. Sapphire includes several editor classes for you to choose
from. In this article we will use the editor class that's specialized for the case where you are editing an XML
file and you want to have an editor page rendered by Sapphire along with an XML source page.

Finally, we need to register the editor. There are a variety of options for how to do this, but covering
all of these options is outside the scope of this article. For simplicity we will register the editor as the default
choice for files named "bugs.xml".

That's it. We are done creating the editor. After launching Eclipse and creating a bug.xml file, you should
see an editor that looks like this:

Sapphire really shines in complex cases like this where form UI is sitting on top a source file that users
might edit by hand. In the above screen capture, what happened is that the user manually entered "BETA2" for the
product stage in the source view. There is a problem marker next to the property editor and the blue
assistance popup is accessible by clicking on that marker. The problem message is displayed along with additional
information about the property and available actions. The "Show in source" action, for instance, will immediately
jump to the editor's source page and highlight the text region associated with this property. This is very
valuable when you must deal with large files. These facilities and many others are available out of the box with
Sapphire with no extra effort from the developer.

Conclusion

Now that you've been introduced to what Sapphire can do, compare it to how you are currently writing UI
code. All of the code presented in this article can be written by a developer with just a few weeks of
Sapphire experience in an hour or two. How long would it take you to create something comparable using
your current method of choice?